Method and apparatus for controlling a multimedia conference by an application server

ABSTRACT

The present invention relates to a method and apparatus for controlling a multimedia conference by an application server, the method includes: in the multimedia conference, the application server divides the m-line in a received terminal session description protocol (SDP), message into two SDPs according to the type of media, and sends them respectively to an audio-video media server and a data media server, or assembles SDPs returned by the audio-video media server and the data media server into one SDP, and sends it to a terminal. The apparatus includes an application server, and the application server includes an SDP dividing module and an SDP assembling module. This invention simplifies the process of signaling interaction, reduces the consumption of the signaling interaction; better synchronizes the controlling of the conventional audio-video media and the data media, makes the realization of the multimedia client more simple; meanwhile, is compatible with the terminals traditionally not supporting data media.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application of InternationalApplication No. PCT/CN2009/072722, filed Jul. 10, 2009, which claims thebenefit of Chinese Patent Application No. 200810068468.9, filed Jul. 11,2008, both of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to the multimedia conference technology ofthe IP Multimedia Subsystem (IMS), network or the Next GenerationNetwork (NGN) network or the Internet network, in particular to a methodand apparatus for controlling a multimedia conference by an applicationserver (AS).

BACKGROUND OF THE INVENTION

The traditional multimedia conference mostly refers to an audio-videoconference, wherein even though some multimedia conferences haverealized the function of a data conference, from the point of view ofrealization and signaling, the data conference and the audio-videoconference are still independent, and the functions of the dataconference and the audio-video conference are fused only from the pointof view of users. One important reason for leading to such a realizationway is that the audio-video media server and the data media server areindependent, and it is hard to fuse those two together, therefore thereis almost no any mature media server (MS) which can realize bothaudio-video media service and data media server. As shown in FIG. 1, itis the schematic diagram of the networking structure of multimediaconference system of the prior art, comprising a SIP (Session InitiationProtocol) soft terminal, a SIP hard terminal, an PSTN (Public SwitchedTelephone Network) terminal, a core network, an AS, an audio-video MSand a data MS. The AS is the control center of the whole conferencesystem, which is directly connected to two MSs, connected to theterminals through the core network, controls the interaction between theterminals and the MSs at the signaling level, and completes a multimediaconference call. The SIP is employed both between the AS and the corenetwork and between the AS and the MSs.

SUMMERY OF THE INVENTION

The technology problem to be solved by the present invention is toprovide a method for controlling a multimedia conference by an AS in amultimedia conference system, and to provide an apparatus forcontrolling the multimedia conference, the present invention simplifiesthe process of signaling interaction, reduces the consumption of thesignaling interaction, makes the realization of multimedia terminalsmore simple; meanwhile, is compatible with the terminals traditionallynot supporting data media.

According to one aspect of the present invention, a method forcontrolling a multimedia conference by an AS is provided.

The method for controlling a multimedia conference by an AS according tothe present invention comprises: in the multimedia conference, the ASdivides m-line in a received terminal session description protocol, SDP,message into two SDPs according to the type of media, and sends themrespectively to an audio-video media server and a data media server, orassembles SDPs returned by the audio-video media server and the datamedia server into one SDP, and sends it to a terminal.

When the conference initiating terminal of the multimedia conferenceinitiates the conference, the method specifically comprises thefollowing steps:

Step 21, the AS parses the SDP sent by the conference initiatingterminal, obtains the m-line of the audio-video media and the datamedia, and classifies the m-line;

Step 22, the SDP sent by the initiating terminal is divided into two ormore SDPs according to the classification of the m-line, the presentinvention takes dividing into two SDPs as an example, one of the twoSDPs is an audio-video SDP, the other one is a data media SDP, and theyare respectively sent to the audio-video media server and the data mediaserver; it is to be noted that the case of dividing into more than 2SDPs is also fallen into the scope of the present invention.

Step 23, when the AS has received one SDP returned by one media server,and not yet received another SDP returned by the other media server, theAS saves the SDP of the former media server and waits for the SDP of thelatter media server, and extracts the SDP of the former media serverwhen receiving the SDP of the latter media server;

Step 24, the AS assembles the SDPs returned by the audio-video mediaserver and the data media server into one SDP, and sends it to theconference initiating terminal.

When the conference initiating terminal of the multimedia conferenceneeds to call a member, the method specifically comprises the followingsteps:

Step 31, the AS sends a SIP message to the member terminal, and obtainsthe SDP of the member terminal;

Step 32, the AS parses the SDP sent by the member terminal, obtains them-line of the audio-video media and the data media, and classifies them-line;

Step 33, the SDP sent by the member terminal is divided into two SDPsaccording to the classification of the m-line, and the two SDPs are sentrespectively to the audio-video media server and the data media server;

Step 34, when the AS has received one SDP returned by one media server,and not yet received another SDP returned by the other media server, theAS saves the SDP of the former media server and waits for the SDP of thelatter media server, and extracts the SDP of the former media serverwhen receiving the SDP of the latter media server;

Step 35, the AS assembles the SDPs returned by the audio-video mediaserver and the data media server into one SDP, and sends it to themember terminal transparently.

After the multimedia conference has been successfully initiated, if theconference initiating terminal needs to switch off a type of conferencemedia channel, then step 24 is further followed by the following steps:

Step 41, the conference initiating terminal sets the port of the m-linecorresponding to the media channel to be switched off in the SDP to be0, and sends it to the AS via the SIP message;

Step 42, the AS compares the media type of the received SDP with themedia type of the conference currently in progress, and extracts them-line with the port being 0 in the SDP, forms one new SDP, and sendsthe new SDP to a corresponding media server to notify it to switch offthe corresponding media channel;

Step 43, the AS assembles the SDPs of the two media serverscorresponding to a member terminal into one new SDP, sends it to themember terminal to notify it to switch off the corresponding mediachannel, and extracts the m-line corresponding to the media server ofthe media channel to be switched off in the SDP of the member terminal,forms one new SDP, and sends it to the corresponding media server; theport of the m-line corresponding to media type to be switched off in thenew SDP is 0.

After the multimedia conference has been successfully initiated, if theconference initiating terminal needs to add a type of media channel,then step 24 is followed by the following steps:

Step 51, the AS switches on the media channel corresponding to the mediaserver with the port of the m-line being 0, according to the SDP sent byconference initiating terminal;

Step 52, the AS notifies the member terminal supporting the type ofmedia to switch on the corresponding media channel.

The method for dividing SDP is:

first extracting the session description portion of the SDP sent by theconference initiating terminal, copying it directly to the divided SDPas the session description portion; then classifying the m-line of theSDP transmitted by the conference initiating terminal into an m-line setof audio-video media and an m-line set of data media according to themedia type, and copying the m-line set of audio-video media and them-line set of data media respectively to the corresponding divided SDPsas the media description portion.

The method for assembling SDP is:

first extracting the session description portion of the SDP returned bythe audio-video media server as the session description portion of anassembled SDP, then according to the order of the m-line in the SDP ofthe conference initiating terminal, assembling the m-line of the SDPreturned by the audio-video media server and the data media server asthe media description portion of the assembled SDP, if there is nocorresponding m-line in the SDP returned by the audio-video media serveror the data media server, setting the port of the m-line to be 0.

In the method, for the terminal without data media capability, the ASmerely interactively negotiates with the audio-video media servercorresponding to the terminal during the whole media negotiationprocess.

In the method, if one media type needs to be switched off by theconference initiating terminal, the AS directly sends an ending messageto the corresponding media server, and uses the SDP of the other mediaserver to form an SDP, in which the port of the m-line of the media typeof a switched-off media server is 0, sends the SDP to the conferenceinitiating terminal, then switches off the media type corresponding toeach member; if the whole conference needs to be switched off by theconference initiating terminal, the AS sends an ending message to allmedia servers, and forms an SDP with all ports of m-line being 0 andtransmitting it to the conference initiating terminal, then sends anending message to each member and the media server corresponding to it.

According to another aspect of the present invention, an apparatus forcontrolling the multimedia conference is provided.

The apparatus for controlling a multimedia conference according to thepresent invention comprises an application server, and the applicationserver further comprises an SDP dividing module and an SDP assemblingmodule, the SDP dividing module is used to divide the SDP sent by aterminal into two SDPs according to the classification of the m-line;the SDP assembling module is configured to assemble the SDPs returned byan audio-video media server and a data media server into one SDP.

Based on the SIP protocol, the present invention provides a solution, inwhich the AS controls the audio-video MS and the data MS at the sametime, through assembling divided SDPs. This invention simplifies theprocess of signaling interaction, reduced the consumption of thesignaling interaction; better synchronizes the controlling of thetraditional audio-video media and the data media, makes the realizationof the multimedia client more simple, meanwhile, is compatible with theterminals traditionally not supporting data media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the networking structure of amultimedia conference system;

FIG. 2 is a flow chart of the signaling when a conference initiatingterminal requests to initiate a conference and switch off a type ofconference media channel;

FIG. 3 is a flow chart of an AS processing a member when the AS invitesthe member to join a conference and the conference initiating terminalswitches off a type of media channel; and

FIG. 4 is a block diagram of the principle of the apparatus of thepresent invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be further detailed hereinafter in connectionwith the drawings and preferred embodiments.

Method Embodiments

According to the embodiment of the present invention, a method forcontrolling a multimedia conference by an AS is provided. FIG. 2 is theflow chart of the signaling when a conference initiating terminalrequests to initiate a conference and switch off a type of conferencemedia channel. Referring to FIG. 2, further detailed description will bemade on particular realization of the AS during the processing of eachsignaling thereinafter:

1, the conference initiating terminal sends out a conference initiatingrequest through an Invite message whose SDP carries the media type(audio, video, application, wb) of the conference that the conferenceinitiating terminal intends to initiate; the AS saves the SDP of themessage after receiving the Invite message, then parses it to obtain them-line of the SDP, and classifies the m-line into audio-video type(audio, video) and data type (application, wb), the SDP is divided intotwo new SDPs according to the classification, the divided SDP shares thesame session description portion with the original SDP, and the m-lineof the original SDP is divided into the two new SDPs according to theclassification;

2, the AS transmits the SDP with the m-line being (audio, video) to anaudio-video MS through the Invite message;

3, simultaneously with the above Action 2, the AS transmits the SDP withthe m-line being (application, wb) to a data MS through the Invitemessage;

4, the audio-video MS first returns an answer SDP through a 183 message,the AS saves the SDP after receiving it and blocks the flow fromcontinuing at the same time, so as to wait for the answer SDP from thedata MS.

When the media negotiation needs distributing and assembling, becausethe two MSs are two different devices, their SIP signaling needs to besynchronized, the AS executes synchronization according to the SDPstatus (Send Offer, Recv Answer) of each MS and SIP signaling. When theAS sends an Invite message containing SDP to individual MSs, if both MSsreturn the 183 message containing an answer SDP or a 200 OK messagecontaining an answer SDP, then the two answer SDPs, when being received,will be directly assembled, and a same SIP message (183 or 200 OK) isused to send the answer SDP to the terminal; if the first MS returns a200 OK message containing SDP, then the AS waits for another answer SDPof another MS, if the SIP message returned by the second MS is differentfrom that by the first MS, i.e., the message returned by the second MSis a 200 OK message containing an answer SDP, then after receiving the200 OK message containing an answer SDP returned by the second MS, theAS sends a PRACK message to the first MS to notify to continue the flow.After the first MS returns the 200 OK message containing an answer SDP,the assembly is performed, and the 200 OK message is used to send ananswer SDP to the terminal.

5, the data MS returns an answer SDP through a 183 message, the ASassembles the received SDP and the saved SDP from the audio-video MSaccording to the order of m-line in the SDP of the conference initiatingterminal;

the method for assembling the SDP comprises: first extracting thesession description portion of the answer SDP returned by theaudio-video MS as the session description portion of the assembled SDP,then assembling the m-line of the answer SDPs returned by theaudio-video MS and the data MS into the media description portion of theassembled SDP according to the order of the m-line in the SDP of theconference initiating terminal, wherein if the answer SDP returned bythe audio-video MS or the data MS has no corresponding m-line, then theport of the m-line is set to be 0;

6, the AS sends the assembled SDP in Action 5 as an answer SDP to theterminal through a 183 message, and resumes the flow relating to theaudio-video MS;

7-12, the AS negotiates with the conference initiating terminal and theMS to complete the signaling flow of PRACK/200 OK;

13, the conference initiating terminal completes resource reservation,and sends an Update message to inform the AS that the resourcereservation has been completed, and the AS processes the SDP in a waysimilar with that in Action 1 upon receiving the Update message;

14-15, as Actions 2-3, the AS sends the SDP of the conference initiatingterminal to the audio-video MS and the data MS via the Update message;

16-18, as Actions 4-6, the AS assembles the answer SDPs, which arereturned by the audio-video MS and the data MS through a 200 OK message,and sends an assembled answer SDP to the conference initiating terminalthrough the 200 OK message;

19, the audio-video MS first issues a final response of 200 OK message,and the AS blocks the flow from continuing upon receiving the response,so as to wait for a final response from the data MS;

20-21, the negotiation between the AS and media devices has beensuccessful after the AS received the final response of 200 OK messagefrom the data MS, and the AS sends the final response of 200 OK messageto the conference initiating terminal; 22-24, the final response isacknowledged by an ACK message;

25, the conference initiating terminal needs to switch off the type ofwb media channel and sends ReInvite message to the AS, wherein theconference initiating terminal indicates the intention through the portnumber being 0 in m=wb parameter of the SDP contained in the ReInvitemessage; after receiving the SDP, the AS compares it with the previousSDP to obtain the media channel that the conference initiating terminalintends to switch off, however, m=wb media channel is data media type,thus the AS merely needs to negotiate with the data MS; the AS updatesthe saved SDP of the conference initiating terminal, and meanwhileextracts the data media type from the SDP to assemble one new SDP;

26, the AS sends the SDP assembled in Action 25 via a reInvite messageto the data MS in order to notify the wb media channel to switch off;

27, upon receiving the answer SDP returned by the data MS via the 200 OKmessage, the AS assembles the negotiated SDP of the audio-video MS andthe received SDP of the data MS into an SDP for answering the conferenceinitiating terminal;

28, the AS answers the conference initiating terminal with the assembledSDP in Action 27 via the 200 OK message;

29-30, the conference initiating terminal and the AS send an ACK messageto acknowledge the 200 OK message, and the media negotiation ofswitching off the media channel between the conference initiatingterminal and the MS is completed.

FIG. 3 is the flow chart of the AS processing a member when the ASinvites the member to join a conference and the conference initiatingterminal switches off a type of media channel.

1, the AS invites a member by sending an Invite message without SDP tothe member terminal;

2, the member terminal returns an offer SDP through a 183 messagecontaining all supported media types; the AS, upon receiving the offerSDP returned by the member terminal, first saves the SDP, then extractsthe m-line of the offer SDP which is consistent with the type of theheld conference according to the media type of the conference which iscurrently held, divides these m-line into audio-video type (audio,video) and data type (application, wb), and assembles them into two newSDPs;

3-4, the AS delivers the two SDPs constructed in Action2 to anaudio-video MS and a data MS via the Invite message respectively;

5, the audio-video MS first returns 183 message containing answer SDP,the AS saves the SDP and blocks the signaling flow from continuing, soas to wait for the answer SDP returned by the data MS;

6, the data MS returns the 183 message containing answer SDP, the ASconstructs the SDPs returned by the audio-video MS and the data MS intoan answer SDP which is returned to the member terminal, and in the casethat there is no m-line in the SDPs of the both MSs, the AS sets itsport to be 0;

7, the AS sends the constructed SDP to the terminal through a PRACKmessage;

8-14, the system completes the acknowledgement process of the response183 message;

15-20, as Actions 13-18 shown in FIG. 2, after the user terminalresource reservation has been successful, the AS acknowledges it andnegotiates with the two MSs;

21-23, the invited member terminal rings and the AS receives a ringingmessage from the member terminal;

24-27, the MS returns a final response of 200 OK message, and the ASsends an ACK message for acknowledgement;

28-29, the member picks up, and the member terminal returns the finalresponse of 200 OK message, and the AS sends an ACK message foracknowledgement;

30, after the conference initiating terminal successfully switches offthe type of media channel with m=wb, the AS needs to notify each memberterminal to switch off the wb media channel of itself through theprocesses in which by using the received negotiated SDP of the memberterminal as a template, the AS assembles the negotiated SDPs of theaudio-video MS and the data MS, to construct one SDP answering themember terminal, wherein the wb port therein is set to be 0, then theassembled SDP is sent to the member terminal through the Invite message,so as to inform the terminal that the wb media channel has been switchedoff;

31, the AS shall inform the data MS while informing the member terminal,the AS extracts the m-line of data type from the member negotiated SDP,and sets the wb port therein to be 0, to construct one new SDP, andsends it to the data MS via the Invite message so as to notify the dataMS to switch off the wb media channel corresponding to the member;

32-33, after receiving an answer SDP returned by the data MS through the200 OK message, the AS updates the saved SDP, and then directly returnsan ACK message without negotiation;

34-35, after receiving the answer SDP responded by the member terminal,the AS updates the saved SDP of the member terminal, then directlyreturns an ACK message.

FIGS. 2 and 3 show the processing executed by the AS during conference'snormal holding and adding or deleting a media stream, wherein theprocess of adding one media channel or a media type is similar to thatof the conference initiating terminal holding a conference and invitinga member to join in the conference, thus omitted herein. Some terminals,for example, the traditional PSTN telephone, do not support dataconference, and therefore, when inviting such terminal to join in aconference, it is only possible for the terminal to join in anaudio-video conference. When a terminal without data media capability isinvited to join in a conference having data media, the AS selects amedia device to negotiate with it according to a media capabilitycontained in the offer SDP provided by the terminal. During the wholeprocedure of the media negotiation, the AS controls the terminal tointeractively negotiate merely with the audio-video MS, so as to realizethe compatibility with the terminal without data capability.

Apparatus Embodiments

According to the embodiment of the present invention, an apparatus forcontrolling multimedia conference is provided. FIG. 4 is the blockdiagram of the principle of the apparatus of the present invention. Asshown in FIG. 4, an AS comprises an SDP dividing module and an SDPassembling module, wherein, the SDP dividing module is configured todivide the m-line of the SDP sent by a terminal into two SDPs accordingto the media type; and the SDP assembling module is configured toassemble the SDPs returned by an audio-video media server and a datamedia server into one SDP.

Obviously, those skilled in the art shall understand that theabove-mentioned modules and steps of the present invention can beimplemented with general computation devices, and can be integrated inone computation device or distributed in the network formed by aplurality of computation devices, alternatively implemented with programcodes executable by computation devices, which can be stored in memorydevices for execution by the computation devices, or implemented withICs, or several modules or steps can be implemented with a single IC.Thus, the present invention is not limited to any particular hardwareand software combination.

Above description is merely to illustrate the preferred embodiments butnot to limit the present invention. Various alterations and changes tothe present invention are apparent to those skilled in the art. Thescope defined in claims shall comprise any modification, equivalentsubstitution and improvement within the spirit and principle of thepresent invention.

What is claimed is:
 1. A method for controlling a multimedia conferenceby an application server, AS, comprising: in the multimedia conference,the AS dividing m-lines in a received terminal session descriptionprotocol, SDP, message into two SDP messages according to the type ofmedia, and sending them respectively to an audio-video media server anda data media server, or assembling SDP messages returned by theaudio-video media server and the data media server into one SDP message,and sending it to a terminal wherein when the conference initiatingterminal of the multimedia conference initiates the conference, themethod specifically comprises the following steps: the AS parsing theSDP message sent by the conference initiating terminal, obtaining them-lines of the audio-video media and the data media, and classifying them-lines; dividing the SDP message sent by the conference initiatingterminal into two or more SDP messages according to the classificationof the m-lines, and sending them respectively to the audio-video mediaserver and the data media server; when the AS has received one SDPmessage returned by one of the audio-video media server and the datamedia server, and not yet received another SDP message returned by otherone of the audio-video media server and the data media server, savingthe SDP message of the one of the audio-video media server and the datamedia server and waiting for the SDP message of the other one of theaudio-video media server and the data media server, and extracting theSDP message of the one of the audio-video media server and the datamedia server when receiving the SDP message of the other one of theaudio-video media server and the data media server; the AS assemblingthe SDP messages returned by the audio-video media server and the datamedia server into one SDP message, and sending it to the conferenceinitiating terminal; wherein after the multimedia conference has beensuccessfully initiated, if the conference initiating terminal needs toswitch off a type of conference media channel, then after the ASassembling the SDP messages returned by the audio-video media server andthe data media server into one SDP message, and sending it to theconference initiating terminal, the method further comprises thefollowing steps: the conference initiating terminal setting the port ofthe m-lines corresponding to the media channel to be switched off in theSDP message to be 0, and sending it to the AS via the SIP message; theAS comparing the media type of the received SDP message with the mediatype of the conference currently in progress, and extracting the m-lineswith the port being 0 in the SDP message, forming one new SDP message,and sending the new SDP message to a corresponding media server tonotify it to switch off the corresponding media channel; the ASassembling the SDP messages of the two media servers corresponding to amember terminal into one new SDP message, sending it to the memberterminal, to notify it to switch off the corresponding media channel,and extracting the m-lines corresponding to the media server of themedia channel to be switched off in the SDP message of the memberterminal, forming one new SDP message, and sending it to thecorresponding media server; the port of the m-lines corresponding tomedia type to be switched off in the new SDP message is
 0. 2. The methodfor controlling a multimedia conference by an application serveraccording to claim 1, wherein when the conference initiating terminal ofthe multimedia conference needs to call a member, the methodspecifically comprises the following steps: the AS sending a sessioninitiation protocol, SIP message to the member terminal, and obtainingthe SDP message of the member terminal; the AS parsing the SDP messagesent by the member terminal, obtaining the m-lines of the audio-videomedia and the data media, and classifying the m-lines; dividing the SDPmessage sent by the member terminal into two SDP messages according tothe classification of the m-lines, and sending the two SDP messagesrespectively to the audio-video media server and the data media server;when the AS has received one SDP message returned by one of theaudio-video media server and the data media server, and not yet receivedanother SDP message returned by other one of the audio-video mediaserver and the data media server, saving the SDP message of the one ofthe audio-video media server and the data media server and waiting forthe SDP message of the other one of the audio-video media server and thedata media server, and extracting the SDP message of the one of theaudio-video media server and the data media server when receiving theSDP message of the other one of the audio-video media server and thedata media server; the AS assembling the SDP messages returned by theaudio-video media server and the data media server into one SDP message,and sending it to the member terminal transparently.
 3. The method forcontrolling a multimedia conference by an application server accordingto claim 1, wherein after the multimedia conference has beensuccessfully initiated, if the conference initiating terminal needs toadd a type of media channel, then after the AS assembling the SDPmessages returned by the audio-video media server and the data mediaserver into one SDP message, and sending it to the conference initiatingterminal, the method further comprises the following steps: the ASswitching on the media channel corresponding to the media server withthe port of the m-lines being 0, according to the SDP message sent byconference initiating terminal; the AS notifying the member terminalsupporting the type of media to switch on the corresponding mediachannel.
 4. The method for controlling a multimedia conference by anapplication server according to claim 1, wherein the method for dividingSDP message is: first extracting the session description portion of theSDP message sent by the conference initiating terminal, copying itdirectly to the divided SDP message as the session description portion;then classifying the m-line of the SDP message transmitted by theconference initiating terminal into an m-line set of audio-video mediaand an m-lines set of data media according to the media type, andcopying the m-lines set of audio-video media and the m-lines set of datamedia respectively to the corresponding divided SDP messages as themedia description portion.
 5. The method for controlling a multimediaconference by an application server according to claim 1, wherein themethod for assembling SDP message is: first extracting the sessiondescription portion of the SDP message returned by the audio-video mediaserver as the session description portion of an assembled SDP message,then according to the order of the m-lines in the SDP of the conferenceinitiating terminal, assembling the m-lines of the SDP message returnedby the audio-video media server and the data media server as the mediadescription portion of the assembled SDP, if there is no correspondingm-lines in the SDP message returned by the audio-video media server orthe data media server, setting the port of the m-lines to be
 0. 6. Themethod for controlling a multimedia conference by an application serveraccording to claim 1, wherein in the method, for the terminal withoutdata media capability, the AS merely interactively negotiates with theaudio-video media server corresponding to the terminal during the wholemedia negotiation process.
 7. The method for controlling a multimediaconference by an application server according to claim 1, wherein in themethod, if one media type needs to be switched off by the conferenceinitiating terminal, the AS directly sending an ending message tocorresponding one of the audio-video media server and the data mediaserver, and using the SDP message of other one of the audio-video mediaserver and the data media server to form an SDP message, in which theport of the m-lines of the media type of a switched-off media server is0, sending the SDP mesaage to the conference initiating terminal, thenswitching off the media type corresponding to each member; if the wholeconference needs to be switched off by the conference initiatingterminal, the AS sending an ending message to all media servers, andforming an SDP message with all ports of m-lines being 0 andtransmitting it to the conference initiating terminal, then sending anending message to each member and the media server corresponding to it.8. The method for controlling a multimedia conference by an applicationserver according to claim 1, wherein the method for dividing SDP messageis: first extracting the session description portion of the SDP messagesent by the conference initiating terminal, copying it directly to thedivided SDP message as the session description portion; then classifyingthe m-lines of the SDP message transmitted by the conference initiatingterminal into an m-lines set of audio-video media and an m-lines set ofdata media according to the media type, and copying the m-lines set ofaudio-video media and the m-lines set of data media respectively to thecorresponding divided SDP messages as the media description portion. 9.The method for controlling a multimedia conference by an applicationserver according to claim 2, wherein the method for dividing SDP messageis: first extracting the session description portion of the SDP messagesent by the conference initiating terminal, copying it directly to thedivided SDP message as the session description portion; then classifyingthe m-lines of the SDP message transmitted by the conference initiatingterminal into an m-lines set of audio-video media and an m-lines set ofdata media according to the media type, and copying the m-lines set ofaudio-video media and the m-lines set of data media respectively to thecorresponding divided SDP messages as the media description portion. 10.The method for controlling a multimedia conference by an applicationserver according to claim 1, wherein the method for assembling SDPmessage is: first extracting the session description portion of the SDPmessage returned by the audio-video media server as the sessiondescription portion of an assembled SDP message, then according to theorder of the m-lines in the SDP message of the conference initiatingterminal, assembling the m-lines of the SDP message returned by theaudio-video media server and the data media server as the mediadescription portion of the assembled SDP message, if there is nocorresponding m-lines in the SDP message returned by the audio-videomedia server or the data media server , setting the port of the m-linesto be
 0. 11. The method for controlling a multimedia conference by anapplication server according to claim 2, wherein the method forassembling SDP message is: first extracting the session descriptionportion of the SDP message returned by the audio-video media server asthe session description portion of an assembled SDP message, thenaccording to the order of the m-lines in the SDP message of theconference initiating terminal, assembling the m-lines of the SDPmessage returned by the audio-video media server and the data mediaserver as the media description portion of the assembled SDP message, ifthere is no corresponding m-lines in the SDP message returned by theaudio-video media server or the data media server , setting the port ofthe m-lines to be
 0. 12. An apparatus for controlling a multimediaconference, comprising an application server, AS, further comprising asession description protocol, SDP, dividing module and an SDP messageassembling module, the SDP message dividing module is configured todivide the SDP message sent by a terminal into two SDP messagesaccording to the classification of the m-lines; the SDP assemblingmodule is configured to assemble the SDP messages returned by anaudio-video media server and a data media server into one SDP messagewherein when the conference initiating terminal of the multimediaconference initiates the conference, the method specifically comprisesthe following steps: the AS parsing the SDP message sent by theconference initiating terminal, obtaining the m-lines of the audio-videomedia and the data media, and classifying the m-lines; dividing the SDPmessage sent by the conference initiating terminal into two or more SDPmessages according to the classification of the m-lines, and sendingthem respectively to the audio-video media server and the data mediaserver; when the AS has received one SDP message returned by one of theaudio-video media server and the data media server, and not yet receivedanother SDP message returned by other one of the audio-video mediaserver and the data media server, saving the SDP message of the one ofthe audio-video media server and the data media server and waiting forthe SDP message of the other one of the audio-video media server and thedata media server, and extracting the SDP message of the one of theaudio-video media server and the data media server when receiving theSDP message of the other one of the audio-video media server and thedata media server; the AS assembling the SDP messages returned by theaudio-video media server and the data media server into one SDP message,and sending it to the conference initiating terminal; wherein after themultimedia conference has been successfully initiated, if the conferenceinitiating terminal needs to switch off a type of conference mediachannel, then after the AS assembling the SDP messages returned by theaudio-video media server and the data media server into one SDP message,and sending it to the conference initiating terminal, the method furthercomprises the following steps: the conference initiating terminalsetting the port of the m-lines corresponding to the media channel to beswitched off in the SDP message to be 0, and sending it to the AS viathe SIP message; the AS comparing the media type of the received SDPmessage with the media type of the conference currently in progress, andextracting the m-lines with the port being 0 in the SDP message ,forming one new SDP message, and sending the new SDP message to acorresponding media server to notify it to switch off the correspondingmedia channel; the AS assembling the SDP messages of the two mediaservers corresponding to a member terminal into one new SDP message,sending it to the member terminal, to notify it to switch off thecorresponding media channel, and extracting the m-lines corresponding tothe media server of the media channel to be switched off in the SDPmessage of the member terminal, forming one new SDP message, and sendingit to the corresponding media server; the port of the m-linescorresponding to media type to be switched off in the new SDP message is0.